The present disclosure is directed towards systems and methods for treating tissue of a body and more particularly, towards approaches designed to treat a natural joint and conditions involving the patella specifically.
A joint is the location at which two or more bones make contact. They are constructed to allow movement and provide mechanical support, and are classified structurally and functionally. Structural classification is determined by how the bones connected to each other, while functional classification is determined by the degree of movement between the articulating bones. In practice, there is significant overlap between the two types of classifications.
There are three structural classifications of joints, namely fibrous or immovable joints, cartilaginous joints and synovial joints. Fibrous/Immovable bones are connected by dense connective tissue, consisting mainly of collagen. The fibrous joints are further divided into three types: sutures which are found between bones of the skull; syndesmosis which are found between long bones of the body; and gomphosis which is a joint between the root of a tooth and the sockets in the maxilla or mandible.
Cartilaginous bones are connected entirely by cartilage (also known as “synchondroses”). Cartilaginous joints allow more movement between bones than a fibrous joint but less than the highly mobile synovial joint. Synovial joints have a space between the articulating bones for synovial fluid. This classification contains joints that are the most mobile of the three, and includes the knee and shoulder. These are further classified into ball and socket joints, condyloid joints, saddle joints, hinge joints, pivot joints, and gliding joints.
Joints can also be classified functionally, by the degree of mobility they allow. Synarthrosis joints permit little or no mobility. They can be categorized by how the two bones are joined together. That is, synchrondoses are joints where the two bones are connected by a piece of cartilage. Synostoses are where two bones that are initially separated eventually fuse together as a child approaches adulthood. By contrast, amphiarthrosis joints permit slight mobility. The two bone surfaces at the joint are both covered in hyaline cartilage and joined by strands of fibrocartilage. Most amphiarthrosis joints are cartilaginous.
Finally, diarthrosis joints permit a variety of movements (e.g. flexion, adduction, and pronation). Only synovial joints are diarthrodial and they can be divided into six classes: 1. ball and socket—such as the shoulder or the hip and femur; 2. Hinge—such as the elbow; 3. Pivot—such as the radius and ulna; 4. condyloidal (or ellipsoidal)—such as the wrist between radius and carps, or knee; 5. Saddle—such as the joint between carpal thumbs and metacarpals; and 6. Gliding—such as between the carpals.
Synovial joints (or diarthroses, or diarthroidal joints) are the most common and most movable type of joints in the body. As with all other joints in the body, synovial joints achieve movement at the point of contact of the articulating bones. Structural and functional differences distinguish the synovial joints from the two other types of joints in the body, with the main structural difference being the existence of a cavity between the articulating bones and the occupation of a fluid in that cavity which aids movement. The whole of a diarthrosis is contained by a ligamentous sac, the joint capsule or articular capsule. The surfaces of the two bones at the joint are covered in cartilage. The thickness of the cartilage varies with each joint, and sometimes may be of uneven thickness. Articular cartilage is multi-layered. A thin superficial layer provides a smooth surface for the two bones to slide against each other. Of all the layers, it has the highest concentration of collagen and the lowest concentration of proteoglycans, making it very resistant to shear stresses. Deeper than that is an intermediate layer, which is mechanically designed to absorb shocks and distribute the load efficiently. The deepest layer is highly calcified, and anchors the articular cartilage to the bone. In joints where the two surfaces do not fit snugly together, a meniscus or multiple folds of fibro-cartilage within the joint correct the fit, ensuring stability and the optimal distribution of load forces. The synovium is a membrane that covers all the non-cartilaginous surfaces within the joint capsule. It secretes synovial fluid into the joint, which nourishes and lubricates the articular cartilage. The synovium is separated from the capsule by a layer of cellular tissue that contains blood vessels and nerves.
Various maladies can affect the joints, one of which is arthritis. Arthritis is a group of conditions where there is damage caused to the joints of the body. Arthritis is the leading cause of disability in people over the age of 65.
There are many forms of arthritis, each of which has a different cause. Rheumatoid arthritis and psoriatic arthritis are autoimmune diseases in which the body is attacking itself. Septic arthritis is caused by joint infection. Gouty arthritis is caused by deposition of uric acid crystals in the joint that results in subsequent inflammation. The most common form of arthritis, osteoarthritis is also known as degenerative joint disease and occurs following trauma to the joint, following an infection of the joint or simply as a result of aging.
Unfortunately, all arthritides feature pain. Patterns of pain differ among the arthritides and the location. Rheumatoid arthritis is generally worse in the morning; in the early stages, patients often do not have symptoms following their morning shower.
Maladies that can affect the knee joint specifically include patellar or kneecap pain, misalignment or dislocation. Pain can exist when there is an excess of force contact between the patella and femur. This can be due to misalignment associated arthritis or anatomical conditions specific to an individual. Kneecap dislocation occurs when the triangle-shaped patellar bone covering the knee moves or slides out of place. This problem usually occurs toward the outside of the leg and can be the result of patella misalignment due to patient specific anatomy or osteoarthritis, or from trauma.
The patella rests in the patellofemoral groove, a cavity located on the knee between the distal femur and the tibia. The sides of the patella attach to certain ligaments and tendons to stabilize and support it. The upper border of the patella attaches to the common tendon of the quadriceps muscles. The side or medial borders of the patella are attached to the vastus medialis muscle, and the lower border of the patella is connected by the patellar ligament to the tibial tuberosity. The main ligament stabilizer, the patellofemoral ligament, rests directly over the femur and the patella while the lateral and medial collateral ligaments acts as the secondary ligament stabilizers from either side of the patella.
Arthritis of the patella is one of the many causes of knee pain. Patella femoral arthritis, is identified when loss of cartilage behind the patella leads to pain in the knee. The pain typically worsens when a patient walks hills, goes up or down stairs, or does deep knee flexion. Arthritis of the patella can result from an injury to the knee joint, ordinary wear and tear, or most commonly the improper tracking of the patella on the femur when the patella does not line up properly.
Non-surgical treatments for patella femoral arthritis include exercises, anti-inflammatory drugs, weight loss, pain medication and cortisone shots to help lessen the pain. External braces or taping to improve patella tracking can also be used. However, if sufficient bone loss occurs, surgery may be necessary.
Surgical options include cartilage shaving, cartilage excision, drilling into subchondral bone to induce regeneration or a lateral release where a tendon is cut to help align the knee. Other surgical options include a tibial tuberosity osteotomy, partial knee replacement and a total knee replacement, or removal of the patella entirely.
In a tibia tuberosity osteotomy, the bump on which your patellar tendon attaches (tibial tuberosity) is moved surgically by cutting the bone and adding plates and/or pins. The tibial tuberosity is moved up, down, left or right depending on the location of the damaged cartilage to move the load on the cartilage to a part of the knee that is still healthy—assuming there is such an area.
In a patellectomy the patella is removed outright. Sometimes this works, but sometimes removing the patella may hasten the onset of arthritis in the rest of the knee. A patella replacement may also be performed where part or all of the patella is replaced with an implant.
Recently, less conventional approaches to treating the patella have been proposed. In one approach, a patellar implant is placed below a patellar tendon to elevate or tilt the patellar tendon. This consequently may alter patellar tracking and decrease forces on the patella to thereby alleviate pain caused by the patella contacting the femur or tibia or by decreasing force loads across the patella-femoral joint.
In a related approach, improper force distributions associated with the patella are addressed by displacing tissues in order to realign force vectors and alter movement across loading the knee joint. Here, again, an objective is to lessen the force with which the patella is pressed against the femur during the gait cycle.
Sufficient attention does not appear to have been given in prior patella treatment approaches, however, to treatment of the knee joint throughout its full range of motion. There is also a need for avoiding negative remodeling of the patellar ligament as well as approaches to maintain a desired alignment of an implant and target tissue.
Therefore, what is needed and heretofore lacking in prior attempts to treat joint pain associated with patella misalignment or dislocation is an implantation method and implant device which addresses full range of joint movement, and which maintains desired structural integrity of anatomy forming the knee joint.
The present disclosure addresses these and other needs.